goddard space flight center 9 th lisa symposium, 23 may 2012 kenji numata laser development for...

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Laser Development for Gravitational-Wave Interferometry in Space

Kenji Numata1,2, Jordan Camp2

1Department of Astronomy, University of Maryland, College Park, Maryland, 20742, USA

2NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Outline

o 1. Introduction– GSFC’s space laser history and recent trends

o 2. Master oscillator– Planar waveguide external cavity diode laser (PW-ECL)

o 3. Pre-amplifier– Low-risk component

o 4. Power amplifier– Noise and qualification tests

o 5. Summary

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

1. Introduction

o NASA/GSFC space laser history– Nd:YAG laser altimeters

o Recent activities and trends– Advanced laser altimeter (ICESat2, LIST, etc.)

• Yb fiber + Waveguide amp.

– Gas sensing lidar (ASCENDS, etc.)• Er fiber + Waveguide amp., stabilized seed laser• Parametric amplification

– Laser communication (LCRD, etc.)• Er fiber amp., telecom fiber components

– Interferometry (NGO/SGO, OpTIIX, etc.)

• Fiber & waveguide technologies wherever possible

MESSENGER/MLA - Mercury(2004-2012)Nd:YAG laser, >0.5B shots to date

LRO/LOLA - moon(2008-2012)Nd:YAG laser, 1+ Billion shots to date

ICESat/GLAS – Earth(2003-2010)Nd:YAG laser, 1.98 billion shots

MGS/MOLA - Mars(1996 -2000)Nd:YAG laser, 670 million shots

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Space laser for interferometry

o Master oscillator/fiber amplifier (MOFA) configuration– Both 1.0 µm and 1.5 µm

o Fiber/waveguide advantages– High robustness, high efficiency, small mass & size, easy cooling– Reliability data available (Telcordia) for many components– Reliable pump source at 97x ~ 980 nm for amplifier– New technologies become available

* Modulator, isolator, redundant LDs are not shown.

OpTIIX, GRACE-FO (1.54µm) NGO/SGO (1.06µm) MO+Preamplifier package

MO + Pre-amplifier Power amplifier

Master Oscillator

Pump LD(MM)

Gain fiber

Pump LD(SM)

Gain fiberWDM TFB~10mW ~100mW~2W

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

2. Master Oscillator

o Looking into various possibilities– Non-planar ring oscillator (NPRO)

• Best high-freq. noise performance. Legacy device.

– Fiber laser• Ring design (GSFC), DBR design (NP photonics)• Large relaxation oscillation

– Planar-waveguide external cavity laser (PW-ECL)• Semiconductor laser• Simplest, smallest, and most cost-effective• Best noise performance at low frequency

10-1

10

1

10

3

10

5

10

7

10

9

Fre

qu

ency

no

ise

[Hz/

rtH

z]

10-4 10

-2 100 10

2 104 10

6

Frequency [Hz]

Reference (master) laser

Stabilized Freerun

NGO requirement

K. Numata, 10.7452/lapl.201210034

DBR FL under thermal cycle test

Ring FL and its frequency noise performance NPRO and PW-ECL package comparison

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

PW-ECL features & status

o Features– Semiconductor gain chip + Planar lightwave circuit (PLC)

• Design details open to NASA

– C-band (~1550nm), ~10mW output– Conversion to 1064nm underway

• Gain chip material change• Awarded SBIR contract to RIO for $750K (3/2012 ~ 9/2013)• NGO/SGO and other lidar applications

o Passed all space qualification tests– No performance degradation by

• Gamma, low/high energy proton, vacuum thermal cycling, pyro shock

0.40

0.30

0.20

0.10

0.00

-0.10Opt

ical

pow

er c

hang

e [d

B]

706050403020100

Dose [kRad]

20MeV 50MeV 50MeV (with shields)

12

10

8

6

4

2

0

Out

put p

ower

[mW

]

8006004002000

Number of cycles

40C -10C

Example result of high energy proton irradiation Example result vacuum thermal cycling

PLC

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

PW-ECL noise performance

o Relative intensity noise (RIN)– Smallest level among any lasers

• No relaxation oscillation peak around MHz range• Shot noise limited above ~100kHz

o Frequency noise– Phase lockable by injection current (100kHz UGF)– Frequency lockable to high finesse cavity and/or hyperfine molecular line

• NGO requirement level demonstrated by 13C2H2 molecule at 1542nm

• Cavity stabilization facility under construction at UT Brownsville (V. Quetschke)

– GSFC funded 1/f noise reduction activity

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

Re

lati

ve

in

ten

sit

y n

ois

e [

/rtH

z]

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

Frequency [Hz]

Shot noise

PW-ECL

NPRO

DBR fiber laser

Littman ECL

DFB LD

102

103

104

105

106

107

Fre

quen

cy N

oise

[Hz/

rtH

z]0.0001 0.001 0.01 0.1 1 10 100 1000

Frequency [Hz]

Freerun Simplified setup Full setup NGO requirement

C. Clivati10.1109/TUFFC.2011.2121

Freerun RIN of various lasers

Freerun freq. noise of various lasers PW-ECL cavity locking PW-ECL molecular line locking

100

101

102

103

104

105

106

107

108

109

Fre

qu

en

cy n

ois

e [H

z/rt

Hz]

10-4

10-3

10-2

10-1

100

101

102

103

104

105

Frequency [Hz]

PW-ECL

NPRO

DFB LD

DBR fiber laser

Littman ECL

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

3.Pre-amplifier

o Design– Single-clad Er- or Yb-doped fiber– Core pump by PM 97x-nm diode– Redundancy addition by polarization combiner

o Noise performance– No significant noise addition– Controllable after amplifier (demonstrated)

o Low risk component– Gamma radiation tests done on 1µm components– Simulation tools, many different vendors available

100

102

10

4

106

10

8

Fre

qu

ency

no

ise

[Hz/

rtH

z]

10-4 10

-2 100 10

2 104

Frequency [Hz]

PW-ECL + EDFA After preamp Before preamp

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

Rel

ativ

e in

ten

sity

no

ise

[/rt

Hz]

10-4 10

-2 100 10

2 104

Frequency [Hz]

PW-ECL + EDFA After preamp Before preamp

Frequency noise before/after pre-amplifier RIN before/after pre-amplifier

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Metrology interferometer for OpTIIX

o PW-ECL + preamp to be flown with OpTIIX – Optical Testbed and Integration on ISS eXperiment

• Technology demonstrator of ATLAST (~16m space telescope)

– Spaceflight of PW-ECL + acetylene cell• Planned launch: ~2015

– Metrology system: heterodyne interferometer (S. Rao)

– <1nm measurement error over hours• Requirement achieved by simplified saturation setup• No external modulator, single pass

Simplified C2H2 locking setup with PW-ECL

Laser truss system concept

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

4.Power Amplifier

o Design– All fiber coupled (tapered fiber bundle)– Large mode area, double-clad Yb fiber– Forward pump to avoid risk and noise sources

• Catastrophic failure can occur with improper implementations

o Noise performance– No additional frequency noise– NGO requirement level

• Differential phase noise (@2GHz)• Stabilized low frequency RIN

10-6

10-5

10-4

10-3

10-2

10-1

Ph

as

e n

ois

e [

cy

cle

/rtH

z]

0.0001 0.001 0.01 0.1 1 10

Frequency [Hz]

Differential phase noise (1.4W output, Liekki fiber) NGO requirement

MM Pump LD Yb LMA DC fiber

TFB>1.4W

Redundant LD

Isolator Input mon. Output mon.90/10

coupler99/1

coupler

From seed>40mW

10-8

2

4

10-7

2

4

10-6

2

4

10-5

Rel

ativ

e in

tens

ity n

oise

[/rtH

z]10

310

410

510

610

710

8

Frequency [Hz]

After amplifier (stabilized) After amplifier (free-run) NPRO (seed) only Shot noise

10-5

10-4

10-3

10-2

10-1

Rel

ativ

e in

tens

ity n

oise

[/rtH

z]

0.0001 0.001 0.01 0.1 1

Frequency [Hz]

After amplifier (stabilized) After amplfiier (freerun) Requirement (LISA)

Differential phase noise RIN and its stabilization (low/high frequency ends)

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Qualification tests on power amp.

o Packaging optimization for TFB– Screening by thermal imager– Proper packaging reduces temperature gradient

o Gamma irradiation on gain fiber– 200 Rads(Si)/min to a total dose of 60 kRads(Si)– Certain brand shows unrecoverable damage

• Probably due to dopants in the core

– Sensitive but no showstopper

o Vacuum thermal cycling– Marginal power/PER degradation at ~1.5W level

60

50

40

30

20

10

0Tem

pera

ture

[C] /

PER

[dB]

131211109876543210

Time [hours]

2.0

1.5

1.0

0.5

0.0

Pow

er [W]

Temperature (left axis) PER (left axis) Power (right axis)

2.0

1.6

1.2

0.8

0.4

0.0

Ou

tpu

t p

ow

er

[W]

4.03.02.01.00.0

Pump power [W]

Nufern fiber Before gamma irradiation After gamma irradiation

2.0

1.6

1.2

0.8

0.4

0.0

Ou

tpu

t p

ow

er

[W]

4.03.02.01.00.0

Pump power [W]

Liekki fiber Before gamma irradiation After gamma irradiation

Vacuum thermal cycling test Gamma on two different Yb fibers

Goddard Space Flight Center 9th LISA Symposium, 23 May 2012Kenji Numata

Summary

o NASA/GSFC has been involved in space-borne laser since 90’s– Actively seeking innovative solutions to meet future science missions’ goals

• Fiber/waveguide technologies to space

– In-house capability to build & test space lasers– Common requirements for all laser instruments

• Lifetime, reliability, and efficiency

o GSFC invested ~$1.2 M over 3 years on LISA laser development– Amplifier development and noise measurements– PW-ECL noise and reliability studies

o Expected to finish qualification of LISA laser by the end of FY13

– System test with 1064nm PW-ECL + pre-amp. + power amp. to be done– 1542nm PW-ECL + Er pre-amplifier to be flown to ISS– No showstopper found